Schwartz-Jampel Syndrome: A Case Report with Clinical and Phenotypic Insights
TL;DR
In early-onset myotonic disorders, SJS should be considered with characteristic craniofacial and skeletal features, and symptomatic treatment with sodium-channel–blocking agents and multidisciplinary rehabilitation may confer functional benefit.
Abstract
Schwartz-Jampel Syndrome (SJS) is a rare autosomal recessive disorder characterised by myotonia, craniofacial dysmorphism and skeletal dysplasia, resulting from pathogenic variants in Heparan Sulfate Proteoglycan 2 (HSPG2). Pathogenic variants disrupt perlecan function, resulting in abnormal cartilage development and impaired neuromuscular transmission. A three-year and fivemonth-old male presented with blepharophimosis, generalised muscle stiffness, delayed motor milestones and gait abnormality. Electromyography demonstrated continuous spontaneous myotonic discharges. Radiographs revealed metaphyseal dysplasia with epiphyseal abnormalities. Molecular testing identified three heterozygous HSPG2 variants with parental carrier status, consistent with compound heterozygosity. Carbamazepine and structured rehabilitation were administered. Follow-up demonstrated reduction in myotonia, improved gait parameters and decreased fall frequency. In early-onset myotonic disorders, SJS should be considered with characteristic craniofacial and skeletal features. Symptomatic treatment with sodium-channel–blocking agents and multidisciplinary rehabilitation may confer functional benefit.